Orange nanowire light-emitting diodes

ABSTRACT

Embodiments of the present disclosure describe a white light illumination system using InGaN-based orange nanowires (NWs) LED, in conjunction with a blue LD for high speed optical wireless communications. By changing the relative intensities of an ultrabroad linewidth orange LED and narrow-linewidth blue LD components, a hybrid LED/LD device achieves correlated color temperature (CCT) ranging from 3000 K to above 6000 K with color rendering index (CRI) values reaching 83.1. Orange-emitting NWs LED are utilized as an active-phosphor, while a blue LD was used for both color mixing and optical wireless communications.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of U.S. application Ser.No. 16/686,993, filed on Nov. 18, 2019, which is a continuationapplication of U.S. application Ser. No. 15/674,275, filed Aug. 10,2017, now U.S. Pat. No. 10,480,719, which claims the benefit of andpriority to U.S. Provisional Application No. 62/375,748, filed Aug. 16,2016, each of which are incorporated by reference herein.

BACKGROUND

Group-III-nitride laser diode (LD)-based solid-state lighting devicesare well known, are relatively droop-free compared to otherlight-emitting diodes (LEDs), and are energy-efficient compared to thatof the traditional incandescent and fluorescent white light systems. TheYAG:Ce³⁺ phosphor used in LD-based solid-state lighting, however, islimited by rapid degradation leading to reduction in efficiency and poorperformance. As a result, a need remains for an alternate architecturecapable of sustaining high temperature, high power density, while beingintensity- and bandwidth-tunable for high color-quality.

In considering the development of next generation lighting andcommunication applications, a major goal includes robust and efficienthybrid devices and systems capable of both white light generation andhigh speed optical wireless communications (OWC).

SUMMARY

In general, embodiments of the present disclosure describe white lightgeneration using an InGaN-based orange nanowires (NWs) LED grown onsilicon, in conjunction with a blue LD for high speed optical wirelesscommunications. By changing the relative intensities of an ultrabroadlinewidth orange LED and narrow-linewidth blue LD components, a hybridLED/LD device achieves correlated color temperature (CCT) ranging from3000 K to above 6000 K with color rendering index (CRI) values reaching83.1, a value unsurpassed by the YAG-phosphor/blue-LD counterpart. Inone example, a white-light wireless communication system is implementedusing a blue LD through on-off keying (OOK) modulation to obtain a datarate of 1.06 Gbps. Orange-emitting NWs LED were utilized as anactive-phosphor, while a blue LD was used for both color mixing andoptical wireless communications.

Visible lighting and image projection systems have attractedconsiderable attention because of relatively small foot-prints, longlifetime, stable light-output, low power consumption and heatgeneration, and high-speed modulation capability. The high-speedmodulation characteristic is particularly desirable for optical wirelesscommunications (OWC) devices or systems. Radio frequency (RF)communications, as the primary source of wireless communications, hasexperienced bandwidth limitations due to the recent unprecedentedincrease in demand for higher data rates transmissions. Substitutefrequency bands, especially the unregulated optical frequencies in thevisible region remain a promising alternative to the overburdened RFspectrum. Switching to visible frequencies will also reduce reliance onhardware while providing diverse options of high speed communicationswith large bandwidths.

Research has primarily been focused on indoor applications of OWC. Toachieve white light, most conventional techniques utilize blue LED toexcite yellow phosphor with highest reported luminous efficacy of 265lm/watt, or combining red, green and blue (RGB) LEDs to achieve a broadwhite light spectrum. Phosphor based technique suffers from limitedcontrollability of the yellow phosphor component in producing thedesired white light characteristics. Also, a longer carrier relaxationlifetime in YAG:Ce³⁺ phosphor inhibits GHz communications, unlessspectral-efficient modulation technique is utilized. For example,advanced communications schemes such as wavelength division multiplexing(WDM) and multiple-input and multiple-output (MIMO) have been adoptedwith the RGB LEDs triplet setup to achieve date throughput beyond 3Gbps.

Advancement of the technology further requires an optical device withsignificantly higher efficiency and greater bandwidth. This gap can befulfilled by utilizing laser diodes (LDs) which exhibit efficientelectrical to optical efficiency, narrower linewidth compared to LED andsupport considerably higher parallel data channels with significantlylower interference. Beyond-100-Gbps data rates have been theorized usingoptimized orthogonal frequency-division multiplexing (OFDM) encodingtechnique. By mixing three primary colors (red, green, and blue, i.e.RGB), one can produce white light with varying color temperatures.However, RGB triplets suffer from an inherent drawback of narrowlinewidth which does not fill the visible spectrum, resulting in thepoor rendering of colors of the illuminated object. One known approachutilized the RYGB configuration with very promising results but theyellow optical source utilized was based on sum frequency generationwhich significantly reduces the cost effectiveness of the system.

It is apparent that a new white-lamp architecture for simultaneouslighting and communications should comprise coherent, small linewidthLD-spectrum, and the broad linewidth LED-spectrum. Although, this LED/LDcombination is an attractive solution for high efficiency white lightingand high bandwidth visible light communications (VLC), the developmenthas been impeded by the lack of high-quality material and reducedefficiency in the “green gap”. Also, efficiency droop, a decrease indevice efficiency with increase in operating bias current, has been abottleneck in planar nitride devices. LEDs emitting in green-yellowregime have been demonstrated but the inherent problems of smallerlinewidth (<60 nm), efficiency droop, and lower internal quantumefficiency of the quantum well based planar structures, limit theirdeployment as an efficient yellow-orange-red wavelength source for whitelight generation.

Examples of the present disclosure utilize a nanowires LED for bothintensity and color tunability functions. The novel implementationutilizes a hybrid combination of nanowires-LED and LD, either in theform of discrete components (as further described herein) or monolithicintegration of multiple color nanowires-LED/laser on a silicon chip orrelated substrate. Furthermore, examples of the present disclosureprovide simultaneous implementation of laser and active-phosphor basedon nanowire-LED for concurrent realization of solid-state lighting anddata communications. A system with wide color tunability andsimultaneous LED-laser integration to yield optical wireless datacommunications capability is described herein.

Accordingly, embodiments of the present disclosure describe a hybridillumination system including an InGaN-based orange nanowires LED incombination with a blue LD for high speed optical data communications.

Embodiments of the present disclosure further describe a methodimplementing a white light illumination system including an InGaN-basedorange nanowires LED in conjunction with high speed opticalcommunication.

The details of one or more examples are set forth in the descriptionbelow. Other features, objects and advantages will be apparent from thedescription and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

This written disclosure describes illustrative embodiments that arenon-limiting and non-exhaustive. In the drawings, which are notnecessarily drawn to scale, like numerals describe substantially similarcomponents throughout the several views. Like numerals having differentletter suffixes represent different instances of substantially similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

Reference is made to illustrative embodiments that are depicted in thefigures, in which:

FIG. 1 illustrates a schematic implementation of an illumination andoptical wireless communications system, according to one or moreembodiments of the present disclosure.

FIG. 2(a) illustrates a TEM image of a NWs LED, according to one or moreembodiments of the present disclosure.

FIG. 2(b) illustrates a top view SEM image of a plurality of NWs LEDs,according to one or more embodiments of the present disclosure.

FIG. 2(c) illustrates a perspective SEM image of a plurality of NWsLEDs, according to one or more embodiments of the present disclosure.

FIG. 3(a) illustrates a graphical view of intensity and wavelengthcharacteristics of a NWs LED evaluated using temperature dependentphotoluminescence, according to one or more embodiments of the presentdisclosure.

FIG. 3(b) illustrates a graphical view of intensity and wavelengthcharacteristics of a NWs LED with varying bias currents, according toone or more embodiments of the present disclosure.

FIG. 4(a) illustrates a graphical view of I-V characteristics of orangeNWs LED, according to one or more embodiments of the present disclosure.

FIGS. 4(b) and 4(c) illustrates a graphical view of L-I-Vcharacteristics of a blue LD, according to one or more embodiments ofthe present disclosure.

FIGS. 5(a)-(e) illustrate a graphical comparison between blue LD andblue LED.

FIGS. 6(a) and 6(b) illustrate white light spectra and CRI coordinatesof a comparable system utilizing RG LEDs.

FIGS. 7(a)-(d) illustrate maximum allowable modulation bandwidth, and arelationship between bit error rate and current.

DETAILED DESCRIPTION

The invention of the present disclosure relates to a white light devicearchitecture suitable for illumination and optical wirelesscommunications. In particular, one example of the present disclosureprovides an ultra-broad linewidth orange NWs LED and blue LD combined toachieve both white light generation and optical wireless communication.The architecture of the present disclosure can be applied tonext-generation high efficiency indoor illumination and optical wirelesscommunication systems. In addition, examples of the present disclosurecan provide simultaneous lighting and communications including acoherent, small linewidth LD-spectrum, and broad linewidth LED-spectrum.These examples, however, should not be viewed as limiting, as thedevices of the present disclosure can be used in innumerableapplications, especially with respect to next generation illuminationand communications systems.

One embodiment of the present disclosure utilizes an orange emitting LEDbased on a platform of InGaN/GaN NWs grown on titanium-coated siliconsubstrate, as well as a narrow linewidth laser for simultaneous colormixing for solid state lighting (SSL) and data communications. Whitelight achieved using the NWs-LED/LD device combination yielded a colorrendering index (CRI) beyond 80, surpassing that of the phosphor/blue-LDcombination with CRI of less than 70, and large tunability of correlatedcolor temperature (CCT). By utilizing the blue LD in conjunction withOOK modulation technique, data rates of 1.06 Gbps were obtained. Thishybrid system thus provided performance within the high speed OWCregime.

Accordingly, embodiments of the present disclosure describe white-lightillumination devices with optical wireless communication capabilities,as well as methods of illuminating with high quality white light andcommunicating via optical wireless communications.

Embodiments of the present disclosure describe nanowires (NWs) baseddevices yielding reduced defect density, improved light-extraction witha larger surface to volume ratio, and increased internal quantumefficiency due to a reduced lattice-strain, thus considerably mitigatingefficiency droop.

Embodiments of the present disclosure utilize an orange emitting LEDbased on a new platform of InGaN/GaN NWs grown on titanium-coatedsilicon substrate, as well as a narrow linewidth laser for simultaneouscolor mixing for solid state lighting (SSL) and data communications.White light achieved using the NWs-LED/LD device combination yielded acolor rendering index (CRI) beyond 80, surpassing that of thephosphor/blue-LD combination with CRI of less than 70, and largetunability of correlated color temperature (CCT). By utilizing the blueLD in conjunction with OOK modulation technique, data rates of 1.06 Gbpswere obtained. This hybrid system thus provided performance within thehigh speed OWC regime.

Examples

The orange NWs LED was grown using GEN 930 plasma-assisted molecularbeam epitaxy (PA-MBE) system. Native oxide was removed from a siliconsubstrate using HF—H₂O solution followed by deposition of 100 nm oftitanium (Ti). The silicon (Si) doped gallium nitride (GaN) was firstnucleated at a lower substrate temperature of 500° C. followed by growthat a higher temperature of 600° C. for crystal quality improvement.Nitrogen (N₂) flow was maintained at 1 sccm with RF power set to 350 W.Active region was grown using seven stacks of GaN quantum barrier (8 nm)and InGaN quantum disk (4 nm). The quantum disks were grown at a lowertemperature of 515° C. followed by capping of 2 nm of GaN, to avoiddissociation when ramping up for quantum barrier growth. Indium (In)beam equivalent pressure (BEP) was set at 5×10⁻⁸ Torr while for Gallium(Ga) it was varied between 3×10⁻⁸-6×10⁻⁸ Torr. A 60 nm thickmagnesium-doped GaN was then grown. Titanium nitride (TiN) has been seento form at NWs base at the nucleation site, as confirmed by TEM and XRD,which considerably improves current injection. TiN in conjunction withunderlying Ti layer reflects longer wavelength photons which alsoconsiderably increases light extraction efficiency of the device.

The orange NWs LED was fabricated using standard UV contact lithographyprocess. The NWs were first planarized with parylene, etched back toreveal the p-GaN contact layers, and then deposited with Ni (5 nm)/Au (5nm), which forms an ohmic contact with p-GaN upon annealing. The LEDmesa was then etched and the Ti buffer layer supporting the NWs wasrevealed as the n-contact metal. Then 500 nm of Au pad was sputtered tocomplete the top contact pads.

FIG. 1 describes an implementation of an illumination and communicationssystem where a blue LD 12 is used in conjunction with orange NWs LED 14to generate white light. Blue LD 12 (LP450-SF-15 from Thorlabs)exhibited a nominal spectral linewidth of around 1 nm centered at 447nm. A commercial blue LED with peak emission at ˜460 nm was used tocompare the white light characteristics. The light beam from blue LD 12passes through diffuser 16. A plano-convex lens 18 (LA1951-A) was usedin front of blue LD 12 to collimate the laser beam. A variableattenuator 20 is provided to match transmitter and receiver levels. Toobtain white light, the beam was passed through diffuser 16 (ED1-050-MD)and mixed with light from orange NWs LED 14. The mixed light was thenpassed through plano-convex lens 22 and long pass filter 24. AvalanchePD or spectrometer 30 receives light passing through filter 24. Themixed white light was then measured using the GL Opti-probe attachment,fiber-coupled into the GL Spectis 5.0 Touch spectrometer.

FIG. 1 further describes a schematic of the On-Off KeyingNon-return-to-zero (NRZ-OOK) modulation setup for the orange NWsLED/blue LD architecture for optical wireless communications (OWC) andwhite-light generation. For comparison of white light quality, either aLD or a LED was used to generate blue light and then combined withorange light from NWs LED, without the modulation signal. The whitelight characteristics were measured using GL-Spectis 5.0 Touchspectrometer without the plano-convex lens and long-pass filter (locatedafter the orange NWs LED), and without the avalanche PD or spectrometer30 or digital communication analyzer (DCA-J 86100C) 32.

For modulating the blue LD 12, DC biasing current (I_(bias)) andpeak-to-peak modulation current (I_(pp)) were adjusted to optimize thesignal-to-noise ratio (SNR) of the transmission. The 1.06 Gbps on-offkeying non-return-to-zero (NRZ-OOK) laser modulation was realized with apseudorandom binary sequence (PRBS) generator 34 (Agilent TechnologiesJ-BERT) having a 2¹⁰-1 long words. The 2¹⁰-1 long PRBS pattern wasconsistent with data pattern length found in applications such asGigabit Ethernet, and SATA 1 that use 8b/10b, as well as other relatedencodings. The NRZ-OOK data was electrically pre-amplified with an ultrabroadband amplifier 36 (Picosecond Pulse Labs, 5868) of 28.5 dB gain toincrease the RF signal power and improve the extinction ratio (ER). Thetransmitted NRZ-OOK optical signal was sent to the APD receiver foroptical-to-electrical conversion and error detection measurements usingan Agilent Technologies Digital Communication Analyzer (DCA-J 86100C).

FIG. 2(a) is a transmission electron microscopy (TEM) image of a NWs LED38 sample clearly show the well-defined InGaN quantum disks 40 (whitehorizontal lines) embedded in body of the NWs LED 38 and separated byGaN quantum barriers. The tapered NWs LED 38 nucleate with a small baseand the lateral size gradually increases as growth progresses. This isattributed to the decrease in temperature with NWs LED 38 height thusfavoring lateral growth. In FIG. 2(a), the TEM image of a single taperedNWs LED 38 shows 7 stacks of InGaN quantum disks (white horizontallines) sandwiched in between GaN barrier.

FIG. 2(b) is a top view scanning electron microscope (SEM) image of theInGaN NWs LEDs showing the NWs LED's mean height of 800 nm and lateralsize of 175 nm. FIG. 2(c) shows that the NWs LEDs were mostly verticallyaligned and disjointed with an areal density of 6.8×10⁹ cm⁻² and fillfactor of 90%.

The optical properties the NWs LEDs were evaluated using temperaturedependent photoluminescence (PL) as shown in FIG. 3(a). A broad PLlinewidth of 184 nm was obtained at room temperature and was attributedto the presence of compositional inhomogeneity and alloy disorderingamong the nanowires and across individual quantum disks. Insets showweak S-shape evolution of the peak wavelengths versus temperature forthe two deconvoluted-peaks, which are in the orange-red and far-redcolor regime, respectively.

The ultrabroad linewidth is particularly desirable for generating highCRI white light as evident in the room temperature electroluminescencemeasurement of an orange LED in FIG. 3(b). With further band-fillingeffect in the electronic transitions of the clusters of NWs, theemission peak wavelength and linewidth were found to be 614 nm (orangecolor) and above 120 nm, respectively. In particular, the peak exhibitweak shift with the increase in current injection which is usually thecase for quantum well based InGaN planar devices in the presence of highpolarization fields. This provided evidence of minimized polarizationfields due to smaller crystal volume and inherent lower strain in thenanowires, which nucleate via strain relaxation. As the EL peakcorrelates well with that of PL, a desired broad linewidth emission wasachieved.

FIG. 3(a) discloses PL intensity versus wavelength at room temperaturefitted with 2 Gaussian peaks. The evolution of the peak wavelength(peak) with temperature (T) are shown in the top and bottom insets,respectively.

FIG. 3(b) illustrates EL spectra of the orange NWs LED with varying biascurrent from 5 to 120 mA, showing a blue shift of 10 nm. An inset showsan ultrabroad linewidth of above 120 nm at high injection current, asobtained by integrating the spectrum.

The L-I-V characteristics of the orange NWs LED was characterized atdifferent biases as shown in FIG. 4(a). A turn-on voltage of 4.2 V wasobtained which was relatively larger than its planar counterpart. Thiscould result from the presence of higher contact resistance at the topp-GaN layer and insertion of AlGaN carrier blocking layers. An importantfeature to be noted is that no saturation in power was observed up to 70mA of current injection.

FIGS. 4(b) and 4(c) show the L-I-V characteristics of the blue LD havinga threshold current of 34.0 mA, 22.2% differential efficiency with peakwavelength at 447 nm and linewidth of 1 nm, while the blue LED having aturn on voltage of ˜2.6 V with peak wavelength of 459 nm and linewidthof 16 nm, respectively. Due to optical coupling and optical fiberlosses, the LD shows a flat power response up to injection current of 25mA.

For the white light experiment, the bias current for the blue LD waskept at the optimum operating condition of 39 mA. The intensity level ofthe ultrabroad linewidth orange LED was varied to improve white lightcharacteristics by changing the bias current from 50 mA to 200 mA. Inparallel, the intensity of blue LD was also adjusted using a variableattenuator keeping the bias at 39 mA. It was seen that the white lightcolor temperature drastically changed with the blue light intensity. Forthe blue LED, the intensity was adjusted by varying the voltage. InFIGS. 5(b) and 5(c) the diffused white light spectral characteristics,which correspond to the integrated intensity ratio between the bluelight and orange light, along with the color rendering index (CRI) andthe correlated color temperature (CCT) based on CIE 1931 standard weremeasured with a GL Opti-probe connected to GL Spectis 5.0 Touchspectrometer. When the orange LED was operated at a bias current of 140mA, a CCT value of 4138 K and a CRI of 83.1 were obtained as shown inFIG. 5(b). As compared to the case when using blue LD to excitesingle-crystal YAG phosphor with the resultant linewidth of ˜100 nm, aCRI of mere 58 was reported. The blue laser based white lighting usingorange NWs LED is thus a better candidate for achieving a prominent CRI.

The white light spectra generated using orange LED with blue LD—FIG.5(b), and blue LED-FIG. 5(c) yielded CRI values of 83.1 and 73.4,respectively, with the respective color coordinates and CCT valuesindicated. The white spots in the chromaticity diagrams correspond tothese values. In selecting the best CRI, the injection current for theorange LED was fixed at 50, 100, or 150 mA, while the intensity of theblue component was varied by simply rotating the variable attenuatorwheel in case of LD and by changing the voltage bias for the LED, thusresulting in the progression in CCT as shown in FIGS. 5(d) and 5(e),respectively.

CRI provides a quantitative measure of the degree of a light sourcerevealing the color of an object under consideration, when compared to aPlanckian light source having the same Kelvin temperature. As shown inFIG. 5(c), considerably good white light characteristics can be achievedwith both blue LD and LED. Compared to a Planckian radiator emittingaround 4000 K, the LD light, having smaller linewidth, reveal the colorof an object more faithfully compared to that of a blue LED with a muchwider linewidth. Thus blue LD, compared to LED exhibits higher CRIvalue. Color temperatures were seen to drastically change with bluelight intensity as shown in FIGS. 5(d) and 5(e).

In another experiment, RG LDs component at 532 nm and 640 nm wereintroduced and CRI values above 90 were obtained but at the cost ofcolor temperature which went below 2000 K as shown in FIGS. 6(a) and6(b). This further elucidated the strength of the novel orange NWsLED/blue LD device architecture. FIG. 6(a) illustrates white lightspectra generated using RGB LD and orange LED for the best CRI valuewith the corresponding CRI coordinate (white spot with cross) shown inthe inset. FIG. 6(b) illustrates CRI coordinates achieved by varying theintensities of the RGB LDs or LEDs to change the color temperatures andto achieve the best CRI value as indicated. A CRI of 90.4 was obtainedbut at the cost of poor CCT (1920 K).

High speed data communications capabilities were also analyzed. FIG.7(a) illustrates maximum allowable modulation bandwidth. The smallsignal response at 50 mA DC bias current, i.e. the −3 dB bandwidth ofthe communications system (inclusive of the blue LD, the laser driver,and the APD) is 1.02 GHz. As compared to an LED, this is two orders ofmagnitude enhancement in modulation bandwidth, and therefore the use ofa blue LD serves well in high data rate OWC.

FIG. 7(a) illustrates a relationship between bit error rate (BER) andcurrent. The optimum current of 39 mA was chosen for further BERoptimization by varying the peak-to-peak voltage. The eye diagrams forthe best BER obtained with OOK encoding at FIG. 7 (c) 0.622 Gbps, andFIG. 7(d) 1.06 Gbps.

It is noted that prior to OWC measurement, the modulation performance interms of BER of the blue LD encoded signals was investigated underdifferent bias currents and peak-to-peak voltage as shown in FIG. 7(b)and the inset, respectively, in order to find an optimum operatingpoint. The power reaching the PD was kept constant at 20 μW by using avariable attenuator for the above optimization. An optimized operatingcondition was obtained when the bias current of the blue LD was set to39 mA and the amplitude of the modulating voltage signal to 125 mV asshown in FIG. 6(b). At a lower bias current, clipping of the modulatedsignal was observed, which degraded the BER of the encoded OOK datastream. An overly biased operation also declines the laser throughputresponse, and degrades the high-frequency response which increases thetransmitted BER. By using the system depicted in FIG. 1 and theoptimized operating condition described above, a transmission rate of upto 1.06 Gbps was achieved. The eye diagrams at 0.622 Gbps and 1.06 Gbpsmeasured using an Agilent digital communication analyzer (DCA) are shownin FIGS. 7(c) and 7(d). At 0.622 Gbps and 1.06 Gbps, with thecorresponding BER of 6.4×10⁻⁴ and 1.93×10⁻³ below the forward errorcorrection (FEC) criterion of 3.8×10⁻³, error-free operation wasrealized.

The present disclosure thus describes a white light device architecturebased on ultrabroad linewidth orange NWs LED and <1 nm linewidth blue LDto achieve both white light generation and optical wirelesscommunication (OWC). The PAMBE grown NWs were observed to be verticallyaligned with density, diameter and length of 6.8×10⁹ cm⁻², 175 nm and800 nm, respectively. The emitted spectrum under 120 mA bias current hada peak wavelength of 614 nm with invariant shift as the bias currentincreases. A high data transmission rate of 1.06 Gbps was achievedwithout the need of an optical blue-filter based on NRZ-OOK modulationscheme. At 1.06 Gbps transmission, open eye diagrams and FEC compliantBER of 1.93×10⁻³ were successfully obtained. In addition, colorimetricproperties of the white light source were characterized. At 140 mAinjection current, white light with a CCT of 4138 K and a CRI of 83.1was achieved, a value unmatched by the blue LD—phosphor counterpart. Thedemonstrated ultrabroad linewidth orange NWs LED in conjunction withnarrow linewidth blue LD based white light source will be applicable fornext-generation high-efficiency indoor illumination and optical wirelesscommunications systems.

Other embodiments of the present disclosure are possible. Although thedescription above contains much specificity, these should not beconstrued as limiting the scope of the disclosure, but as merelyproviding illustrations of some of the presently preferred embodimentsof this disclosure. It is also contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of this disclosure. Itshould be understood that various features and aspects of the disclosedembodiments can be combined with or substituted for one another in orderto form various embodiments. Thus, it is intended that the scope of atleast some of the present disclosure should not be limited by theparticular disclosed embodiments described above.

Thus the scope of this disclosure should be determined by the appendedclaims and their legal equivalents. Therefore, it will be appreciatedthat the scope of the present disclosure fully encompasses otherembodiments which may become obvious to those skilled in the art, andthat the scope of the present disclosure is accordingly to be limited bynothing other than the appended claims, in which reference to an elementin the singular is not intended to mean “one and only one” unlessexplicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiment that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Moreover, it is notnecessary for a device or method to address each and every problemsought to be solved by the present disclosure, for it to be encompassedby the present claims. Furthermore, no element, component, or methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the claims.

The foregoing description of various preferred embodiments of thedisclosure have been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit thedisclosure to the precise embodiments, and obviously many modificationsand variations are possible in light of the above teaching. The exampleembodiments, as described above, were chosen and described in order tobest explain the principles of the disclosure and its practicalapplication to thereby enable others skilled in the art to best utilizethe disclosure in various embodiments and with various modifications asare suited to the particular use contemplated. It is intended that thescope of the disclosure be defined by the claims appended hereto

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. An orange nanowire light-emitting diode (LED), comprising: a titanium-coated silicon substrate; and a plurality of InGaN/GaN nanowires grown on the titanium-coated silicon substrate, wherein the InGaN/GaN nanowires comprise a plurality of InGaN quantum disks located between GaN barriers, wherein the InGaN/GaN nanowires are tapered, and wherein a lateral size of the nanowire increases from a base.
 2. The orange nanowire LED of claim 1, wherein the substrate is an n-type silicon substrate.
 3. The orange nanowire LED of claim 1, wherein a base of the plurality of InGaN/GaN nanowires located adjacent to the titanium-coated silicon substrate is nucleated.
 4. The orange nanowire LED of claim 1, wherein the nucleated base of the plurality of InGaN/GaN nanowires comprises titanium nitride (TiN).
 5. The orange nanowire LED of claim 1, wherein the plurality of InGaN/GaN nanowires have a height of approximately 800 nanometers.
 6. A white light illumination and optical wireless communications device, comprising: a blue LD; a modulator connected to modulate current supplied to the blue LD to encode digital data on an output of the blue LD; a plano-convex lens configured to receive the output of the blue LD and to collimate the output of the blue LD; an orange nanowire light emitting diode (LED) as an active phosphor; a diffuser positioned between the plano-convex lens and the based orange nanowire LED to mix the collimated output of the blue LD with light from the orange nanowire LED to generate a white light for illumination while simultaneously the modulated output from the blue LD is utilized for optical wireless communications.
 7. The device of claim 6, further including a variable attenuator located between the plano-convex lens and the diffuser, wherein the attenuator selectively reduces an amplitude of the collimated output of the blue LD.
 8. The device of claim 6, wherein the blue LD has a linewidth of approximately 1 nanometer (nm).
 9. The device of claim 8, wherein the blue LD is centered at approximately 447 nm.
 10. The device of claim 6, wherein the orange nanowire LED is based on a platform of InGaN/GaN nanowires grown on a titanium-coated silicon substrate.
 11. The device of claim 6, wherein the orange nanowire LED comprises: a titanium-coated silicon substrate; and a plurality of InGaN/GaN nanowires grown on the titanium-coated silicon substrate.
 12. The device of claim 11, wherein the plurality of InGaN/GaN nanowires comprise a pluralty of InGaN quantum disks located between GaN barriers.
 13. The device of claim 12, wherein the InGaN/GaN nanowires are tapered, wherein a lateral size of the nanowire increases from a base.
 14. The device of claim 11, wherein a base of the plurality of InGaN/GaN nanowires located adjacent to the titanium-coated silicon substrate is nucleated.
 15. The device of claim 14, wherein the nucleated base of the plurality of InGaN/GaN nanowires comprises titanium nitride (TiN).
 16. The device of claim 6, wherein the white light has a CRI above
 80. 